Compilare: user.cpp: In function ‘int div_N(unsigned int, unsigned int&)’: user.cpp:18:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=2; i*i < N; i ++){ ^ user.cpp:24:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i*i == N){ ^ user.cpp: In function ‘int main()’: user.cpp:31:20: warning: unused variable ‘i’ [-Wunused-variable] unsigned N, d, i; ^